The invention relates to an axial piston machine according to the precharacterising clause of claim 1 or 2.
An axial piston machine of this type is described in DE-A 21 01 213. In this previously known axial piston machine, the restraint device for supporting the retracting device is formed by holding plungers which are mounted to be radially displaceable in radial guide holes in the housing and are prestressed radially inwards by springs, the plungers having at their inner ends oblique faces which are inclined towards the adjacent retracting device relative to the associated radial plane and engaging, with these oblique faces, behind the outer border of a perforated disc forming the retracting device. This known restraint device has the following disadvantages owing to the oblique faces. If the inclination of the oblique faces is too great, there is the risk of the perforated disc pressing the holding plungers outwards owing to the axial tensile force of the pistons, with the result that the holding plungers lose their stability and are able to exert only a reduced restraining force on the perforated disc, or none at all. In such a case, there is the risk of the perforated disc being overstressed by the axial tensile force of the pistons and, for example, warped. It should be borne in mind here that the holding plungers are particularly inclined to yield outwards owing to vibrations which are present when the axial piston machine is in operation and to the radial force components which act on the oblique faces. If, in contrast, the inclination of the oblique faces is too small, there is the risk of the holding plungers jamming on the perforated disc, with the result that the rotary operation would be impaired and, because of wear, an inadequate service life would have to be expected.
Another major disadvantage of the known axial piston machine is that, owing to the fact that they project into the housing interior space, the holding plungers interfere with the mounting or demounting of the components arranged in the housing interior space.
The object on which the invention is based is to construct a restraint device of the type specified at the outset such that reliable functioning and a long service life can be obtained.
This object is achieved by the features of claims 1 or 2.
In the inventive configuration according to claim 1, the restraint device cooperates with a nonrotating component, namely the swash plate, the retracting device cooperating with a supporting device engaging behind it and connected to the swash plate. This gives rise to another support for the retracting device, namely on the swash plate, on which mutual support can be achieved in a simple and stable manner with relatively large supporting areas, with the result that low wear coupled with reliable support is ensured even with a rotating retracting device.
In the configuration according to claim 2, the restraint device is not mounted on the housing, but on the swash plate. This likewise enables the above-described advantages to be achieved, and in addition simple production is possible since the constructional features for the arrangement and mounting of the restraint device on the swash plate can be formed on the latter in a simple and cost-effective manner. This is due not only to the fact that the swash plate is a relatively small component, but is also a component with a high degree of processing, on which the additional features for the arrangement of the restraint device can be realised efficiently in one procedure. claims 3 to 25 contain advantageous developments of the invention.
According to a development of the invention, when the axial piston machine is in operation, the restraint device is displaced in a self-acting manner or automatically from a release position releasing the retracting device into a working position engaging behind the retracting device and, once the operation has been stopped, is automatically displaced into its release position again, the displacement into the working position being effected by the pressure of an adjoining or adjacent pressure space which is present or a pressure line and the displacement into the release position being effected by the force of a spring. By pressurising the restraint device with an internal pressure which is present when the axial piston machine is in operation or an external pressure, for example from an adjacent axial piston machine, it is possible in a simple manner to produce a pushing-in force which is greater than the retracting or pushing-against force required, so that in operation the position of the restraint device in its working position is reliably ensured. Owing to the automatic movement of the restraint device into its release position, it is not necessary, during mounting or demounting, for any special attention to be paid or any adjusting work performed to move the restraint device into its release position. This ensures simple and rapid mounting or demounting, while ensuring a stabilised retracting device and reliable operation.
In the case of an axial piston machine of the present type, suction forces act on the pistons in pump operation or when the axial piston machine in motor operation performs a braking function, which forces try to lift the slide shoes and thus the retracting device off from the swash plate. In the configuration according to the invention, such axial loads are not damaging even if they overload the retracting device, since the latter finds additional support and stabilisation on the restraint device and is able to take up the loads without damage.
The retracting device is to be arranged in the region of the lateral half of the axial piston machine in which the pistons perform a suction stroke, this region extending approximately over 180xc2x0. A restraint device arranged preferably centrically in the region of this lateral half, or a plurality of restraint devices arranged on this lateral half, are, in the case of an axial piston machine adapted for pump operation, also able to function in cases where the axial piston machine performs a motor operation owing to a braking function. In the case of axial piston machines movable in both directions of rotation, one or more restraint devices are to be arranged in each case in the region of the two lateral halves.
A particularly stable support for the retracting device arises when the area on the restraint device provided for the support is a radial area relative to the axis of rotation of the axial piston machine.
An advantageous embodiment for a restraint device is a stop peg of preferably circular cross-section which is mounted to be displaceable in a radial guide hole in the housing between the working position and the release position. It is advantageous to provide the pin in its outer end region with a flange on which a spring, in particular a helical spring, arranged between the flange and an inner hole shoulder is able to engage and pressurise the stop peg into its release position. For the pneumatic or hydraulic displacement of the pin into its working position, the hole space located radially outside relative to the stop peg can be connected by a channel to the housing interior space or to a space exhibiting a pressure when the axial piston machine is in operation. When the hole space is connected to the housing interior space, the channel can run in the housing wall or longitudinally in the stop peg. In order to provide twice the operational reliability or in order to be able to selectively connect the hole space either to the housing interior space or to the pressure space, it is advantageous to provide two corresponding channels, in each of which is arranged a nonreturn valve which automatically closes under the effect of the pressure which becomes established in each case in the pressure space or of a closing spring.
It is furthermore advantageous to arrange, on the relevant lateral half, or on both lateral halves, of the axial piston machine, in each case only one stop peg parallel to the pivot axis of the swash plate. Such a housing design may be selectively used for immovable or movable swash plates. In this case, it is also advantageous to round the stop peg convexly at its side facing towards the retracting device so as to prevent constraints arising in the case of a pivotable swash plate.
It is also advantageous to arrange the stop peg such that between it and the retracting device there is a small spacing which is merely dimensioned to be of such a size that, in the event of an overload and deformation of the retracting device within its elastic range, the retracting device abuts against the stop peg before it is deformed beyond its yield point.
In addition, it is advantageous if the supporting device is actuated by the restraint device such that the supporting device engages behind the retracting device only when the restraint device is situated in its working position, and otherwise releases it. On actuation of the restraint device, therefore, not only is the swash plate anchored in the housing, but additionally it is ensured that the retracting device is secured to the swash plate. In the demounting position, in which the restraint device is not actuated, not only is the swash plate then released relative to the housing, but additionally the securing of the retracting device with respect to the swash plate is released. The demounting can thus be effected without problems. In this configuration, the supporting device may, for example, have a rotary shaft which is interlocked with the restraint device and is rotated on actuation of the restraint device. It is possible to arrange on the rotary shaft an eccentric projection which engages behind or releases the retracting device depending on the rotary position of the rotary shaft.